1. Field of the Invention
The present invention relates to a pellicle for photolithography using a light having a wavelength of at most 200 nm.
2. Discussion of Background
A pellicle is a dustproof integral device to be mounted on a photomask or a reticle (hereinafter they will be referred to as a mask) so as to prevent dust particles from depositing on the mask and to prevent pattern failure during exposure, used in photolithography as one step in production of semiconductor devices or liquid crystal display boards. As its structure, usually a transparent thin membrane bonded to a frame by using adhesives is mounted on the mask at some distance from the mask surface.
In fields of production of semiconductor devices and liquid crystal display panels in which such a pellicle is used, the wavelength of light sources to be used has been shortened rapidly also in photolithography, along with minimization of wiring and wiring interval. In a conventional exposure technique with a minimum pattern dimension of at least 0.3 xcexcm, a process employing an i-beam light source (365 nm) has been mainly used, and as a material of a transparent thin membrane of a pellicle (hereinafter referred to as a pellicle membrane), a cellulose nitrate type material has been used.
In recent years, for a photolithographic patterning process with a minimum pattern dimension of at most 0.3 xcexcm, a KrF excimer laser is being introduced, but its irradiation wavelength is 248 nm, and the cellulose nitrate type membrane material is inadequate in view of durability. Further, it has been found that an amorphous perfluoropolymer is effective as a membrane material in the case where a light having a short wavelength such as an excimer laser is employed (Japanese Patent No. 2951337 or Japanese patent No. 2952962).
On the other hand, for a photolithographic patterning process with a minimum pattern dimension of at most 0.2 xcexcm under development in recent years, as a laser emitting a light having a wavelength of at most 200 nm, use of e.g. an argon fluoride excimer laser emitting a light having a wavelength of 193 nm (hereinafter referred to as an ArF excimer laser) or a fluorine gas excimer laser emitting a light having a wavelength of 157 nm (hereinafter referred to as a F2 excimer laser) has been proposed.
However, since these laser lights have an extremely high energy, even the above amorphous perfluoropolymer as disclosed in Japanese Patent No. 2951337 is inadequate in view of durability. For example, of xe2x80x9cCYTOPxe2x80x9d (Japanese tradename) which is a perfluoropolymer used in the above patent, transmission of light and durability suddenly decrease at a wavelength shorter than 170 nm. This perfluoropolymer has a significantly low transmission of the F2 excimer laser light having a wavelength of 157 nm. Therefore, development of a pellicle membrane which can be used for F2 excimer laser light has been desired.
Moreover, with respect to adhesives for bonding the pellicle membrane to a frame, there are similar problems of degradation due to reflected light or scattering light of the laser. Thus the adhesive having a high durability has also been desired.
The present inventors have found a fluorine-containing polymer having a high durability and a high transmission of a laser light for irradiation which has a wavelength of at most 200 nm (particularly at most 180 nm) (hereinafter referred to as a short-wavelength laser light). The present invention relates to a pellicle employing this fluorine-containing polymer as a pellicle membrane or as an adhesive.
Namely, the present invention provides a pellicle for an exposure treatment by means of a light having a wavelength of at most 200 nm, comprising a frame and a pellicle membrane bonded to the frame by means of an adhesive, wherein the pellicle membrane or the adhesive comprises the following fluorine-containing polymer (A):
fluorine-containing polymer (A): a substantially linear fluorine-containing polymer having a chain of carbon atoms as the main chain, and containing as carbon atoms in its main chain, a carbon atom having one or two hydrogen atoms bonded thereto and a carbon atom having no hydrogen atom bonded thereto and having a fluorine atom or a fluorine-containing organic group bonded thereto.